Whether the organism is a plant or a person, when all systems are in balance and working as they should, that's called homeostasis. Good stuff. When a stimulus causes things to go out of homeostasis, the organism is in a state of stress. Often, that stress is appropriate. Stress can trigger the "fight or flight" reaction necessary for survival from a threat. However, stress that continues over long durations is not healthy, nor is it fun, nor does it make sense for the middle schooler.
I am not a health care professional, so I am not going to dwell either on the many ill effects that can result from sustained stress, nor will I address ways to cope with and remediate stress. But see a health care professional about these things. I also recognize that your experiences in science class can sometimes cause stress, whether it's the stress from worrying about a test, a grade, a dissection of a critter, or the interactions that occur in class. What I am here to say is that if you are experiencing sustained stress, or stress that causes problems for you, hey, let me know. I'll try my best to contain the actions that cause stress for you or your child. I will consider it a serious matter, just as you and your parents should consider continued high levels of stress as a threat to your health and well-being.